1. Field of the Invention
The present invention relates to a driven transmission gear operable to adjust the tension of a drive chain or belt in a motorcycle or the like, and particularly to an anti-turn structure advantageous for use with a tension-adjusting bolt for moving an axle of a drive wheel.
2. Description of the Background Art
It is well known to provide a tension-adjusting bolt to adjust the tension of a chain on a motorcycle or the like. In this case, the axle of a drive wheel is moved by operating a tension-adjusting bolt, thereby increasing or decreasing slack in the drive chain. Also, it is known to provide the axle of a drive wheel with a stride lock. The stride lock is penetrated by the axle and is provided with a slit. The axle extends in the left-right direction of the vehicle. A tension-adjusting bolt passes through the slit portion so as to extend in the front-rear direction of the vehicle. Rotation of the tension-adjusting bolt is permitted by opening the slit through adjusting the fastening force for the axle, and the rotation of the tension-adjusting bolt is stopped by closingly fastening the slit. Such a structure is disclosed, for example, in Japanese Laid-open Patent publication No. 64-67494.
In such a wheel support portion, an anti-turn structure is necessary for preventing the tension-adjusting bolt from being slackened by vibrations. The tension-adjusting bolt is generally fixed by use of a double nut. However, such an approach leads to an increase in the number of component parts by the number relevant to the double nut, and the number of manufacturing steps is increased by the double nut fastening operation.
In addition, according to Japanese Laid-open Patent publication No. 64-67494, the double nut can be omitted, but in this case, the slit is formed in the stride lock is required to have a comparatively high strength for supporting the axle, leading to a lowering in the strength of the stride lock. As a result, it is necessary to raise the strength of the stride lock and other member(s), which, in turn, leads to an increase in the overall weight of the wheel support portion.
In view of the foregoing, it is an object of the present invention to make it possible to omit a double nut without causing an increase in weight in a tension adjustment structure in a wheel support portion of a driven transmission gear.